For connection of electrical modules use is made of cables which are typically connected by means of plug contacts, plug connectors or soldered connections with terminals of an associated electrical module and for this purpose are previously stripped of insulation at the ends. On occasion, cable parts are connected together by splicing devices such as known from, for example, U.S. Pat. No. 4,520,229 A.
EP 1515403 A2 discloses a cable processing machine with a cable advance device and two pivot arms, which can feed the leading and trailing ends of a cable length by means of grippers to processing stations, crimping presses or bush-fitting devices arranged laterally of the cable longitudinal axis. The cable is separated off beforehand by means of separating or stripping knives and stripped of insulation at the ends. In that case attention has to be given avoidance of damage of the electrical conductors by the tool or the stripping knife during the stripping of insulation.
EP 2717399 A1 discloses a method for stripping insulation from a cable extending in longitudinal direction, in which an insulation is cut into by means of stripping knives and subsequently pulled off by displacing the stripping knives in longitudinal direction. During the pulling-off process the longitudinal position of the stripping knives is registered in each instance at the points at which the stripping knives contact the cable conductors. Due to the number of registered longitudinal positions or places of conductor contact the stripped cable has a high quality.
In order to detect contact with conductor a measuring device equipped with a capacitive sensor is used. The capacitive sensor is connected with the stripping knives and constructed in such a way that contact of the conductive knife with the conductor of the cable can be detected on the basis of an increase in capacitance.
FIG. 1 shows a prior art correspondingly designed device 1′ for stripping insulation from cables, which is provided with a measuring device 6 serving for capacitance measurement. For that purpose, the measuring device 6 is connected with the stripping knife 10′ by way of a screened measurement cable 90, plug connector 91 and contacting plate 92. The stripping knife 10′ serves as a first electrode of a capacitor, the second electrode of which is formed by the mass of the stripping device. If during the work process the stripping knife 10′ penetrates the casing or insulation 82 of the processed cable 8 and comes into contact with the electrical conductor 81 the capacitance correspondingly increases. Consequently, through measuring the resulting capacitance changes it is possible to detect contact with the electrical conductor 81 by the stripping knife 10′.
The electrically equivalent circuit diagram of the device 1′ of FIG. 1 with respect thereto is shown in FIG. 2. The stripping knife 10′ has, without cable contact, a capacitance CW relative to ground potential M. The cable 8 or the electrical conductor 81 has a conductor capacitance CL relative to ground potential M. As soon as the stripping knife 10′ contacts the cable conductor 81, the switch S1 shown in FIG. 2 is closed, as a result of which the capacitances CW of the stripping knife 10′ and CL of the cable conductor 81 are added together. If the cable conductor 81 should make contact with the mass (ground potential M) of the stripping device 1′ then the switch S2 shown in FIG. 2 is closed. The capacitor CG represents the basic capacitance of the device 1′.
During operation of the device the measurement cable 90 is moved and deformed by any movement of the stripping knife 10′ connected therewith, which requires a complicated cable guidance and can lead to cable fractures and produce changes in capacitance, which influence the measurement. Insofar as the stripping knife 10′ has to be demounted and reinstalled for servicing and re-equipped purposes then the measurement cables 90 have to be unplugged and plugged back in again on each occasion. This leads to a corresponding expenditure of time and can give rise to errors if the measurement cables 90 are erroneously swapped or no longer plugged in. High-quality plug connectors 91 and screen measurement cables 90 additionally occasion a relatively high outlay of cost and assembly effort for production of the stripping device 1′.
Moreover, the cables connected with the tool impair the mobility of the tool. In particular, multiple rotations in the same axis can hardly be realized.
In the case of stripping devices with rotating parts, particularly rotating knives, there is additionally the problem that a fixed cabling, in technical terms, is barely able to be realized. The stated problems remain regardless of whether the tool is moved linearly or along a curve.
The described problems are not confined to stripping devices, but arise with all devices for processing cables and conductors in which a tool connected with a cable is moved.
EP 1772701 A1 discloses, for example, a device for determining the diameter of the electrical conductor of a cable, which is acted on at a first position by an alternating voltage signal, which is decoupled again at a second position by means of a capacitive sensor and supplied to a measuring device. In order to determine the conductor diameter, displaceably mounted tools, contact elements or contact knives, which are connected with a defined electrical potential by way of a connecting cable, are guided towards the electrical conductor until this is contacted and the alternating voltage signal experiences a change, whereby the conductor diameter can be established.
In the case of this device as well, the cables connected with the tool are subjected to a mechanical loading and occasion corresponding outlay in production and maintenance. The tool is similarly limited in mobility.